1. Field of the Invention
The invention relates to an inhibitor switch.
2. Description of the Related Art
Conventional inhibitor switches are shown, for example, in FIG. 7 of Japanese Patent Laid-Open No. 293228/1996. FIG. 7 shows a perspective view of an inhibitor switch.
As shown in FIG. 7, an inhibitor switch 101 is provided with a terminal block 103, a casing 105 and a moving block 107. The terminal block 103 is provided with a plurality of fixed contacts 109.
The moving block 107 is provided with moving contacts 111. The moving block 107 is supported to be rotatable relative to the terminal block 103 and a casing 105. The moving block 107 is provided with a fitting hole 119, which is fitted onto a manual shaft of an automatic transmission.
A body 121 of the moving block 107 is formed of a resin, and the moving contacts 111 are positioned on and heat clamped on the body 121 to be fixedly joined thereto. An example of such positioning and fixed joining is shown in FIG. 8.
As shown in FIG. 8, the body 121 of the moving block 107, which is generally formed of a resin, is provided with positioning projections 123 for positioning and caulking projections 125 for heat caulking. In FIG. 8, the caulking projections 125 have heads after heat caulking but are in the form of straight projections prior to heat caulking. The moving contacts 111 are provided with positioning holes 127 for positioning and caulking holes 129 for heat caulking. The positioning holes 127 of the moving contacts 111 are fitted onto the positioning projections 123 of the body 121 to be positioned on the body 121, in which state the caulking projections 125 being fitted into the caulking holes 129 of the moving contacts 111 are heat clamped as shown in FIG. 8 such that the moving contacts 111 are fixedly joined to the body 121.
Accordingly, when the terminal block 103 is fixed on a housing of the automatic transmission and the manual shaft is fitted into the fitting hole 119 of the moving block 107 for use, the moving block 107 rotates together with rotation of the manual shaft. Rotation of the moving block 107 causes the moving contacts 111 to slide relative to the fixed contacts 109 so that the moving contacts 111 put the fixed contacts 109 in selective conducting condition at predetermined speed change positions. Accordingly, speed change positions of the automatic transmission can be electrically detected based on the relative rotation positional relationship of the fixed contacts 109 and the moving contacts 111, conformed to rotation of the manual shaft.
Hereupon, the inhibitor switch 101 is mounted inside or outside the housing of the automatic transmission to be under severe conditions exposed to high temperatures. Accordingly, when the body 121 of the moving block 107 is generally formed of a resin, it undergoes some slight deformation or camber at the time of high temperature, which causes rotation of the moving contacts 111 to be behind rotation of the manual shaft, that is, angular hysteresis leading to a limit on enhancement of detection accuracy of speed change positions.
In contrast, it is possible to suppress deformation or camber at the time of high temperature with the use of a resin having an excellent heat resistance, but there has been caused a problem that a product is increased in cost as a whole because such resin is expensive.
Also, since positioning of the moving contacts 111 relative to the body 121 of the moving block 107 is performed by fitting the positioning holes 127 of the metallic fixed contacts 111 onto the positioning projections 123 of a resin provided on the body 121 as shown in FIG. 8, there has been caused a limit in enhancement of accuracy in positioning the moving contacts 111 on the body 121. Further, since fixation of the moving contacts 111 to the body 121 is performed by heat caulking of the caulking projections 125 formed from a resin, not only is it difficult to manage the enhancement of the strength, but a large space is also needed for enhancing the strength in such fixation. In this regard, there is a limitation in ensuring a space in the inhibitor switch 101 which has little spatial margin. Accordingly, enhancement of accuracy in speed change positions has been limited in view of the above-mentioned problems.
The invention has its object to provide an inhibitor switch, of which positional accuracy is further enhanced.
In a first aspect, the invention provides an inhibitor switch comprising a terminal block with fixed contacts, and a moving block which is mounted and fitted onto a manual shaft of an automatic transmission, has moving contacts, and is rotatable relative to the terminal block, and for electrically detecting a speed change position of the automatic transmission on the basis of a relative rotating positional relationship of the fixed contacts and the moving contacts in accordance with rotation of the manual shaft, the moving block having a boss portion formed of a resin and being mounted on the manual shaft, and an arm-shaped contact support portion mounting thereon the moving contacts, the contact support portion being formed of metal and at least a part of the moving contacts being joined to the contact support portion by caulking.
In a second aspect, the invention provides an inhibitor switch according to the first aspect, wherein a positioning projection for positioning is formed on the contact support portion by means of a press, a positioning hole for positioning is formed on at least a part of the moving contacts, and the positioning hole is fitted onto the positioning projection to position at least a part of the moving contacts relative to the contact support portion.
In a third aspect, the invention provides an inhibitor switch according to the second aspect, wherein a caulking projection for caulking is formed on the contact support portion by means of a press, a caulking hole for the caulking is formed on at least a part of the moving contacts, and the caulking hole is fitted onto the caulking projection to effect the caulking.
In a fourth aspect, the invention provides an inhibitor switch according to any one of the first to third aspects, wherein the contact support portion has a joining hole, which is joined to the boss portion circumferentially.
In a fifth aspect, the invention provides an inhibitor switch according to any one of the first to fourth aspects, wherein a part of the moving contacts comprises a signaling contact formed of a leaf spring and the other part of the moving contacts comprises large capacity current-carrying contacts having a larger conductor cross sectional area than that of the signaling contact, the signaling contact is joined to an intermediate portion of the contact support portion by caulking, and a contact receiving portion formed of a resin is provided on a tip end side of the contact support portion farther than a position of the signaling contact and the large capacity current-carrying contacts are received in the contact receiving portion with biasing members therebetween to elastically bias the large capacity current-carrying contacts toward the fixed points.
The invention according to the first aspect comprises a switch housing having a terminal block with fixed contacts and a cover, and a moving block which is mounted and fitted onto a manual shaft of an automatic transmission, has moving contacts, and is rotatable relative to the switch housing, and can electrically detect a speed change position of the automatic transmission on the basis of a relative rotating positional relationship of the fixed contacts and the moving contacts in accordance with rotation of the manual shaft.
The moving block also has a boss portion formed of a resin and mounted on the manual shaft, and an arm-shaped contact support portion mounting thereon the moving contacts. The contact support portion is formed of metal and at least a part of the moving contacts can be joined to the contact support portion by caulking. Accordingly, since the contact support portion is formed of metal, thermal deformation is suppressed even when circumstances in use are at high temperature, whereby rotation of the manual shaft can be correctly followed. Thereby, angular hysteresis, in which rotation of the moving contacts deviates relative to rotation of the manual shaft, is suppressed, so that enhancement in the detection accuracy of speed change positions can be attained.
Also, since at least a part of the moving contacts is joined to the contact support portion formed of a metal plate by caulking, accuracy in positioning is made easier than in the case of being formed of a resin, and joining strength can be enhanced without the need of much space. Accordingly, accuracy with respect to speed change positions can be enhanced from such points.
In addition to the effect achieved by the invention of the first aspect, according to the invention of the second aspect, the positioning hole of the moving contacts can be fitted onto the positioning projection of the contact support portion to position at least a part of the moving contacts relative to the contact support portion. Besides, the positioning projection for positioning can be formed on the contact support portion by means of a press, and thus formation of the positioning projection of high accuracy makes it possible for the moving contacts to be positioned relative to the contact support portion with good accuracy. Accordingly, accuracy in the detection of speed change positions can be enhanced.
In addition to the effect achieved by the invention of the second aspect, according to the invention of the third aspect, the caulking hole in the moving contacts is fitted onto the caulking projection of the contact support portion to enable performing caulking joining. Besides, the caulking projection for caulking can be formed on the contact support portion by means of a press, and thus control of the caulking projection is facilitated and the joining strength can be greatly enhanced without the need of much space. Accordingly, accuracy in the detection of speed change positions can be enhanced.
In addition to the effect achieved by the invention of any one of the first to third aspects, according to the invention of the fourth aspect, the contact support portion can have a joining hole joined to the boss portion circumferentially. Accordingly, the metallic contact support portion is securely joined to the boss portion of a resin so that the contact support portion can correctly rotate following the rotation of the manual shaft through the boss portion. Accordingly, accuracy in the detection of speed change positions can be further enhanced.
In addition to the effect achieved by the invention of any one of the first to fourth aspects, according to the invention of the fifth aspect, the large capacity current-carrying contacts are supported on a tip end side of the contact support portion farther than a position of the signaling contact, so that a circumferential contact spacing defined on the fixed contacts, of which ON and OFF are detected with elastic contact by the large capacity current-carrying contacts can be ensured to be large in association with a lever ratio. Being greater in contact pressure than that with the signaling contact, the large capacity current-carrying contacts are liable to produce abrasion powder at the time of sliding, so that when circumferential spacings of the fixed contacts are small, the possibility that failure in conduction caused by abrasion powder present between the fixed contacts becomes high. However, failure in conduction can be suppressed by ensuring large circumferential spacings of the fixed contacts in association with the lever ratio.
The positional accuracy on the outer peripheral side is enhanced by forming the contact support portion from a metal, so that accuracy in detection of ON and OFF of the large capacity current-carrying contacts can be greatly enhanced.
The large capacity current-carrying contacts for current-carrying to the starter motor and the like are larger in contact pressure and conductor cross sectional area than the signaling contact, and as such are not easily supported directly on the metallic arm shaped contact support portion. However, the contact receiving portion formed of a resin is provided on a tip end side of the contact support portion to be able to easily support the large capacity current-carrying contacts.
Also, the boss portion and the large capacity current-carrying contacts provided on the tip end side of the arm-shaped contact support portion are interposed between the terminal block and the casing to enable putting the contact support portion in a center state. So, contact pressure can be stabilized even when the signaling contact supported midway through the contact support portion is formed of a leaf spring.